Background: Epinephrine(adrenaline) has been used in advanced life support in cardiac arrest since the early 1960s. Despite the routine recommendation for its use, evidence to support administration is less than ideal. Although it is clear from multiple observational studies that epinephrine improves return of spontaneous circulation (ROSC) and short-term survival, most evidence suggests an absence of improvements in survival with good neurologic outcomes. In cardiac arrest we want to take advantage of the alpha effects of epinephrine, including peripheral vasoconstriction, and therefore increasing aortic diastolic pressure, which in turn helps augment coronary and cerebral blood flow. On the other hand, we want to avoid the potentially detrimental beta effects including dysrhythmias, decreased microcirculation, and increased myocardial oxygen demand all of which increase the chances of recurrent cardiac arrest and decreased neurologic recovery. The only two interventions in cardiac arrest that have shown improve survival with good neurologic outcomes continue to be high-quality CPR and early defibrillation. The debate over the utility of epinephrine in OHCA has been ongoing for several years now and many providers have been awaiting the results of the PARAMEDIC-2 trial that was just published in the NEJM 2018.

What They Did: Prehospital Assessment of the Role of Adrenaline: Measuring the Effectiveness of Drug Administration in Cardiac Arrest (PARAMEDIC-2).This was a multicenter, randomized, double-blind, placebo controlled trial involving 8014 patients with OHCA in the United Kingdom

Patients were well balanced at baseline and had similar concurrent treatments

Limitations:

Hospital-based care, including targeted temperature management, hemodynamic support, ventilatory criteria, and prognostication were not specified in the trial protocol, but did follow national guidelines

Used only 1mg epinephrine q3 – 5min, whereas other dosing strategies might have produced different results

No data on patients baseline neurologic status

The original protocol anticipated a higher survival rate than the one that was observed (6.5% in the placebo group and 7% in the epinephrine group) àSee discussion for elaboration

Information about the quality of CPR was limited to the first 5 minutes of cardiac arrest and involved <5% of enrolled patients

Discussion:

The evidence to date of survival to hospital discharge or long term survival from prior observational studies:

Algorithms for Resuscitation and Post-ROSC Care:

There was a low rate of shockable rhythms in this study (19.2% in Epi arm and 18.7% in the placebo arm). This is evidenced by the extremely low survival rate in this study of 3.2% and 2.4% respectively. However, this is interesting because the authors removed 615 patients who survived after initial management (ie defibrillation -> ROSC). This critique seems to be very prevalent on twitter and should be squashed. Survival was low because those most likely to survive, were removed from study.

CPR was performed in witnessed cardiac arrest in almost 70% of cases

Median time from emergency call to ambulance arrival at the scene was quite quick at about 6 ½ minutes

Median time between emergency call and administration of trial agent 21 minutes.This is an important point, as cardiac arrest is believed to have 3 phases: First 5 min = Electrical Phase (Heart Most Amendable to Defib), Next 10 – 15min = Circulatory Phase, and >20min = Metabolic Phase (Acid-Base Derangements). Epinephrine seems to have its best chances of effect at <20min.

Supraglottic airways were commonly used in this trial in approximately 70% of cases

As per prior observational trials [2 – 9] the use of epinephrine did seem to increase the chances of ROSC (36.3% vs 11.7%).

The authors also make the astute point that number of patients who would need to be treated with epinephrine to prevent one death after cardiac arrest was 112 in this study, but this should also be compared to the things that make a difference in neurologic outcomes which include, CPR performed by a bystander (NNT = 15) and early defibrillation (NNT = 5)

Author Conclusion:“In adults with out-of-hospital cardiac arrest, the use of epinephrine resulted in a significantly higher rate of 30-day survival than the use of placebo, but there was no significant between-group difference in the rate of a favorable neurologic outcome because more survivors had severe neurologic impairment in the epinephrine group.”

Clinical Take Home Point: In this well done, multicenter trial epinephrine given at 1mg q3 – 5 minutes increased the chances of ROSC but came at a cost of more ICU usage, more patients with severe neurological disabilities, and no difference in survival with favorable neurological outcome compared to placebo. The use of epinephrine 1mg q 3 – 5 minutes should no longer be part of standard cardiac arrest protocols. Epinephrine should be administered on a case by case basis by experienced providers who perceive that there is a benefit to be had.

Hi Emily,
This has been my strategy for the past year. epi drip titrated to DBP 35 – 45mmHg. Unfortunately, there is no hard data to support this, but it seems to make more physiologic sense. Although I would argue that the data for 1mg epi q3-5min with the addition of this trial shows increased ROSC & short-term survival at the expense of worsened neuro outcomes (i.e. Harm > Benefit IMHO). Hope this helps.

For patients with shockable rhythms were they given amio as well? If so, did that effect the results?

Why didn’t they also show # of pts w/ ROSC were shocked? # of Pts w/ ROSC were w/ shockable rhythms. Just asking give epi if pt has shockable rhythm, was shocked, given amio. If in PEA, exclude epi if epi was not effective at all?

Hello Michael,
I have the same information available to me as you do. As best I can tell the authors removed 615 patients who survived after initial management (ie defibrillation -> ROSC). It is unclear if they received amiodarone or not. It looks like of the patients that remained in the study, 14.5% in epi group and 9.2% in the placebo group received amiodarone. Maybe an email to the authors?

Hi Andrew,
Not sure about the answer to this. Reading through the supplement I don’t see any comments about dilution of the epinephrine. Therefore I assume there was no dilution of the epi used in this trial.

[…] demonstrated that epinephrine may improve ROSC but not neurologically intact survival in OHCA. You can see an extensive list at REBEL EM where they also have a recent review of this trial. Although guidelines still have epinephrine […]